Polyethylene is commercially produced in a variety of ways. Catalysts based on chromium and related polymerization processes are described in U.S. Pat. No. 2,825,721. The chromium catalysts and the corresponding polymerization processes have wide spread acceptance in the polymerization and copolymerization of ethylene. Slurry processes in which the catalyst, the monomer or monomers and a diluent are subjected to polymerization conditions for the monomers are known in the art.
Many homopolymers of ethylene and copolymers of ethylene and other olefins have been described, produced and sold. In recent years, so called linear low density polyethylenes have been marketed. While the original low density polyethylenes were characterized by long chain branching as well as short chain branches and thus were not linear, the modern low density polyethylenes are linear polymers, i.e. they have essentially no long chain branching but contain short chain branching introduced into the molecule by a comonomer such as 1-butene which produces ethyl branches. The quantity and kind of such short side chains have influence on the physical properties of the polymers produced.
One process for the production of linear low density polyethylene is through copolymerization of ethylene and other 1-olefins such as 1-butene in a gas phase polymerization utilizing a catalyst which comprises a silica support containing chromium, titanium and fluorine deposited thereon as described in U.S. Pat. No. 4,011,382. 1-hexene is mentioned in this patent as a possible comonomer. Efficient production of linear low density polyethylene and improving the respective processes are remaining goals in the industry.